Open house information can be entered in the MLS and seen by agents (and the public, if your MLS offers a public view). To advertise an open house for a listing, from the Listings pull-down menu, choose View/Revise Your Listings, select the appropriate listing, and then click Open House Dates. Enter the appropriate information and click Submit.
NOTE: The Open Houses button that is accessible to the public displays open houses scheduled within the next two weeks (or other time period, as specified by your MLS), if your MLS offers a public view of listing data.
See also
Cancelling an open house in the MLS